Transmitter apparatus

ABSTRACT

A transmitter apparatus capable of reducing the distortions of vector modulated waves. This apparatus includes variable coefficient filters ( 110,112 ) in a stage preceding an amplitude signal voltage generating part ( 104 ) and also includes variable coefficient filters ( 111,113 ) in a stage preceding a phase modulated wave generating part ( 105 ). These variable coefficient filters ( 110 - 113 ) are used to perform a pulse shaping, thereby adjusting the delay between an amplitude component modulated signal (r(t)) and a phase component modulated signal (SC(t)) whereby a resolution, which is finer than the sampling period of a signal processing, can be used to adjust the delay time difference between the amplitude component modulated signal (r(t)) and the phase component modulated signal (SC(t)). As a result, the distortions of vector modulated waves (Srf(t)) can be reduced to a sufficiently small level.

TECHNICAL FIELD

The present invention relates to a transmitting apparatus thatsynthesizes an envelope signal and a phase modulation signal andtransmits the result as a vector modulation wave.

BACKGROUND ART

A power amplifier provided in the output section of a transmittingapparatus in a wireless communication system requires both lowdistortion and efficiency. Power amplifiers are classified intoamplifiers using transistors for the current source or using transistorsfor switching operation. Amplifiers using transistors for the currentsource may be class A amplifiers, class AB amplifiers, class Bamplifiers and class C amplifiers. Further, amplifiers using transistorsfor switching operation may be class D amplifiers, class E amplifiersand class F amplifiers.

Conventionally, in high-frequency power amplifiers that amplifymodulation waves including envelope fluctuation components, class A orclass AB linear amplifiers are used in order to linearly amplifyenvelope fluctuation components. However, there is a drawback that thepower efficiency of linear amplifiers is inferior compared to non-linearamplifiers such as class C amplifiers or class E amplifiers.

As a result, when a conventional linear amplifier is used for a mobiletype wireless apparatus such as a mobile telephone or mobile informationterminal apparatus using a battery as a power source, there is thedrawback that usage time is short. Further, when a conventional linearamplifier is used for a base station apparatus in a mobile communicationsystem provided with a plurality of large power transmissionapparatuses, there is a drawback of causing an increase in the size ofthe base station apparatus and the heating value.

Therefore, as a transmission apparatus with efficient transmissionfunctions, there is a transmission apparatus that attaches an envelopecomponent to a phase modulation wave by dividing a modulation signalinto the amplitude component (envelope component) and the phasecomponent, generating a phase modulation wave with constant envelopefrom the phase component and changing the power supply voltage of anon-linear amplifier according to the envelope component and that causesa vector modulation wave including an envelope fluctuation component.

FIG. 1 illustrates a configuration of a transmitting apparatus as afirst conventional example described above. This transmitting apparatus10 as the first conventional example is formed with transmission datasignal input terminal 11, I signal generating section 13, Q signalgenerating section 14, amplitude signal voltage generating section 15,phase modulation wave generating section 16, power amplifying section 17and transmission output terminal 18. I signal generating section 13 andQ signal generating section 14 form complex envelope computing section12.

In wireless communication system, a transmission signal with informationto be transmitted is transmitted as a modulation wave by means ofamplitude r(t) and phase φ(t) of a carrier wave. In this case, if theangular frequency of carrier wave is ω_(c), modulation wave S(t) to betransmitted to a channel is expressed by the following equation.

S(t)=r(t)·exp[ω_(c) ·t+φ(t)]  (Equation 1)

Here, phase modulation wave S_(c)(t) with a constant envelope isexpressed by the following equation.

Sc(t)=exp[ω_(c) ·t+ω(t)]  (Equation 2)

In the modulation step in signal processing, a transmission data signalis often processed as the I signal I(t) and the Q signal (Q) that arethe in-phase component and quadrature component of complex envelope.These are collectively referred to as “IQ signals” and are expressed bythe following equations.

I(t)=r(t)·cos [φ(t)]  (Equation 3)

Q(t)=r(t)·sin [φ(t)]  (Equation 4)

Further, if an amplitude signal r(t) and a phase signal φ(t) areexpressed by IQ signals, equations are as follows.

r(t)={I(t)² +Q(t)²}^(1/2)   (Equation 5)

φ(t)=tan⁻¹ {Q(t)/I(t)}  (Equation 6)

In FIG. 1, a transmission data signal inputted from transmission datasignal input terminal 11 is converted into an I signal (I)t in I signalgenerating section 13 and a Q signal Q(t) in Q signal generating section14.

Amplitude signal voltage generating section 15 and phase modulation wavegenerating section 16 generate an amplitude signal r(t) and phasemodulation wave S_(c)(t) from the I signal I(t) and the Q signal Q(t),respectively.

Phase modulation wave S_(c)(t) that is a carrier wave having angularfrequency ω_(c) and phase-modulated by the phase signal φ(t), isgenerated in phase modulation wave generating section 16 and inputted topower amplifying section 17.

On the other hand, the amplitude signal r(t) is used to set a powersupply voltage value of power amplifying section 17. The amplitude ofthe output signal of power amplifying section 17 changes according tothe power supply voltage value. That is, the envelope of the outputsignal of power amplifying section 17 changes according to theamplification signal r(t).

As a result, the signal acquired by multiplying power supply voltagevalue r(t) of power amplifying section 17 and phase modulation waveS_(c)(t), which is the output signal of phase modulation wave generatingsection 16, is amplified by gain G of power amplifying section 17, andoutputted as RF vector modulation wave Srf(t). That is, vectormodulation wave Srt(t) is expressed by the following equation.

Srf(t)=G·r(t)·exp [ω_(c) ·t+φ(t)]  (Equation 7)

As described above, the modulation wave to be inputted to the inputterminal of power amplifying section 17 is phase modulation waveS_(c)(t) with a fixed envelope level, and, consequently, an efficientnon-linear amplifier can be used for power amplifying section 17 as ahigh frequency amplifier, so that it is possible to provide a efficienttransmitting apparatus (for example, see Patent Document 1).

FIG. 2 shows a configuration example of amplitude signal voltagegenerating section 15 and phase modulation generating section 16 oftransmitting apparatus 20 in the first conventional example. Inamplitude signal voltage generating section 15, amplitude signalgenerating section 21 computes and generates an amplitude signal r(t) byequation 5 and DA converter 22 generates amplitude signal voltage. Inphase modulation wave generating section 16, phase signal generatingsection 23 computes and generates a phase signal φ(t) by equation 6, DAconverter 24 generates phase signal voltage and phase modulating section25 phase-modulates a carrier wave by the phase signal φ(t) to form phasemodulation wave S_(c)(t).

FIG. 3 is a block diagram for further explanation of the firstconventional example. In FIG. 3, the configurations of I signalgenerating section 13 and Q signal generating section 14 forming complexenvelope computing section 12 are shown in detail.

Recently, many wireless communication systems employ a digitalmodulation scheme. In this case, information to be transmitted is adigital value, and, consequently, a transmission data signal can beexpressed by a discrete-time pulse sequence. However, this pulse shapesignal excessively occupies a wide frequency bandwidth and therefore isgenerally processed as continuous-time, smoothed waveforms I(t) and Q(t)by band-limiting discrete-time pulse shape waveforms Ip(t) and Qp(t) infilters. In this case, for the filter, a pulse shaping filter (forexample, root cosine roll-off filter) that is directed to performingband-limitation while canceling the intersymbol interference betweenpulses, is used.

Therefore, in transmitting apparatus 30 shown in FIG. 3, when I signalgenerating section 13 and Q signal generating section 14 receives asinput a transmission data signal from transmission data signal inputterminal 11, first, pulse generating sections 31 and 32 convert thetransmission data signal into an I component pulse signal Ip(t) and a Qcomponent pulse signal Qp(t), respectively, and pulse shaping filters 33and 34 perform band-limitation and outputs the I signal I(t) and the Qsignal Q(t), respectively.

Although digital filters are generally used for pulse shaping filters 33and 34 in most cases, analogue filters may be used.

Further, when digital filters are used for pulse shaping filters 33 and34, although FIR filters (finite impulse response filters) are generallyused in most cases, IIR filters (infinite impulse response filters) canbe used as well.

For example, when an FIR filter is used and the order of transferfunction is m+1 (i.e., the number of taps is m+1), if the coefficient ofthe transfer function (i.e., tap coefficient) is Ck (here, k is anatural number), the relationship between input signal data sequenceX(n) and output signal data sequence Y(n) can be expressed by thefollowing equation.

Y(n)=C0·X(n)+C1·X(n−1)+ . . . +Cm·X(n−m)   (Equation 8)

By the way, when there is a difference between the time amplitude signalr(t) takes to reach power amplifying section and the time phase signalφ(t) takes to reach power amplifying section 17, distortion occurs invector modulation wave Srf (t), which is the output signal of poweramplifying section 17. This time difference is caused by, e.g., thedifference of delay time in circuits that process an amplitude signalr(t) and a phase signal φ(t).

FIG. 4 is a graph showing frequency spectrum of vector frequency Srf(t)that is the output signal of power amplifying section 17. In the pathsthrough which an amplitude signal r(t) and a phase signal φ(t) reachpower amplifying section 17, if there is no difference between delaytimes, the frequency spectrum shown in FIG. 4A can be acquired, and, ifthere is a difference between the delay times, a frequency spectrumspread (distortion of modulation wave) occurs as shown in FIG. 4B. In afrequency division multiplex communication system where a plurality ofchannels are arranged in the frequency domain, this frequency spectrumspread interferes with adjacent channels and therefore is not desirable.

FIG. 5 is a block diagram showing the configuration of transmittingapparatus 40 employs a configuration correcting the difference betweenthe time amplitude signal r(t) takes to reach power amplifying section17 and the time phase signal φ(t) takes to reach power amplifyingsection 17, as a second conventional example. This transmittingapparatus 40 of the second conventional example provides shift registers41, 42, 43 and 44 in the subsequent stage of pulse shaping filters 33and 34.

Operations of transmitting apparatus 40 of the conventional example willbe explained. In addition to the same operations as in transmittingapparatus 30 of the first conventional example shown in FIG. 3, bydelaying an IQ signal by given time in shift registers 41 to 44,transmitting apparatus 40 of the conventional example delays anamplitude signal r(t) or a phase signal φ(t) by given time. The delaytime is set to the given time by, for example, selecting a given outputstage, by a switch from a plurality of connected registers andextracting a signal. Thus, by adjusting the difference between delaytimes in shift registers 41 and 43 provided on the path to generate anamplitude signal r(t) and the delay time in shift registers 42 and 44provided on the path to generate a phase signal φ(t), and by reducingthe difference between the time amplitude signal r(t) takes to reachpower amplifying section 17 and the time phase signal takes to reachpower amplifying section 17, it is possible to reduce the distortion ofvector modulation wave Srf(t) (e.g., see Patent Document 1).

Patent Document 1: Japanese Patent Application Laid-Open No. Hei 6-54877

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, in transmitting apparatus 40 of the second conventional exampleshown in FIG. 5, the minimum level of change for changing a delay time,which is equivalent to the resolution of adjusting a delay time, is thedelay time per stage in shift registers 41 to 44. This delay time perstage generally corresponds to the sampling period for digital signalprocessing. Therefore, there is a problem that the delay time adjustmentresolution cannot be precise compared to the sampling period of asignal.

The degree where the distortion of vector modulation wave Srf(t) isreduced is decided by the accuracy of adjusting a delay time.Consequently, when the adjustment resolution is limited by the samplingperiod and insufficient, it is difficult to reduce the distortion ofvector modulation wave Srf(t), which is the output of power amplifyingsection 17, to a sufficiently low level.

In view of the above, it is therefore an object of the present inventionto provide a transmitting apparatus that reduces the distortion of avector modulation wave that is a transmission output to a sufficientlylow level.

Means for Solving the Problem

To solve the above problems, the transmitting apparatus of the presentinvention employs a configuration having: a first pulse generatingsection that generates an in-phase component pulse signal; a secondpulse generating section that generates a quadrature component pulsesignal; a first variable coefficient filter that outputs the in-phasecomponent pulse signal as a first in-phase component modulation signal;a second variable coefficient filter that outputs the in-phase componentpulse signal as a second in-phase component modulation signal; a thirdvariable coefficient filter that outputs the quadrature component pulsesignal as a first quadrature component modulation signal; a fourthvariable coefficient filter that outputs the quadrature component pulsesignal as a second quadrature component modulation signal; an amplitudesignal voltage generating section that generates an amplitude componentmodulation signal from the first in-phase component modulation signaland the first quadrature component modulation signal; a phase modulationwave generating section that generates a phase modulation wave from thesecond in-phase component modulation signal and the quadrature componentmodulation signal; and a power amplifying section that generates avector modulation wave acquired by amplitude-modulating the phasemodulation wave in the amplitude component modulation signal.

With this configuration, transfer function coefficient sequences forfirst to fourth variable coefficient filters change, so that it ispossible to realize the function of a pulse shaping filter by first tofourth variable coefficient filters and adjust the delay time differencebetween an amplitude component modulation signal and a phase componentmodulation signal with precise resolution compared to the samplingperiod in signal processing using the pulse shaping function, therebyreducing the distortion of vector modulation waves to a sufficiently lowlevel.

Further, the transmitting apparatus of the present invention employs aconfiguration having: a first pulse generating section that generates anin-phase component pulse signal; a second pulse generating section thatgenerates a quadrature component pulse signal; a first pulse shapingfilter that receives the in-phase component pulse signal as an inputsignal; a second pulse shaping filter that receives the quadraturecomponent pulse signal as an input signal; a first variable coefficientfilter that receives the in-phase component pulse signal as an inputsignal; a second variable coefficient filter that receives thequadrature component pulse signal as an input signal; a first additionoperation section that adds an output signal of the first pulse shapingfilter and an output signal of the first variable coefficient filter andoutputs this added signal as a first in-phase component modulationsignal; a second addition operation section that adds an output signalof the second pulse shaping filter and an output signal of the secondvariable coefficient filter and outputs this added signal as a firstquadrature component modulation signal; an amplitude signal voltagegenerating section that generates an amplitude component modulationsignal using a combination of the first in-phase component modulationsignal and the first orthogonal modulation signal or a combination of anoutput signal of the first pulse shaping filter and an output signal ofthe second pulse shaping filter; a phase modulation wave generatingsection that generates a phase modulation wave using a signal not usedin the amplitude signal voltage generating section in the combination ofthe first in-phase component modulation signal and the first orthogonalmodulation signal or the combination of the output signal of the firstpulse shaping filter and the output signal of the second pulse shapingfilter; and a power amplifying section that generates a vectormodulation wave acquired by amplitude-modulating the phase modulationwave in the amplitude component modulation signal.

With this configuration, transfer function coefficient sequences for thefirst and second variable coefficient filters change, so that it ispossible to adjust the delay the time difference between an amplitudecomponent modulation signal and a phase component modulation signal withprecise resolution compared to the sampling period in signal processingusing the pulse shaping function, thereby reducing the distortion ofvector modulation waves to a sufficiently low level. Further, in thefirst and second variable coefficient filters, the difference componentis produced, which is equivalent to delaying a signal, and added to theoutput signal of the first and second pulse shaping filters, so that itis possible to perform delay adjustment much more accurately or performdelay adjustment with precise resolution compared to the sampling periodin signal processing using variable coefficient filters with a muchsimpler configuration.

Advantageous Effect of the Invention

The present invention enables precise resolution, compared to thesampling period in signal processing, to adjust the delay timedifference between an amplitude component modulation signal and a phasecomponent modulation signal in detail, so that it is possible to reducethe distortion of vector modulation waves to a sufficiently low level.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a transmittingapparatus of the first conventional example;

FIG. 2 is a block diagram showing an example of a configuration of thetransmitting apparatus of the first conventional example;

FIG. 3 is a block diagram showing a detailed configuration of thetransmitting apparatus of the first conventional example;

FIG. 4 illustrates a frequency spectrum of vector modulation waveSrf(t);

FIG. 5 is a block diagram showing a configuration of a transmittingapparatus of a second conventional example;

FIG. 6 is a block diagram showing a configuration of a transmittingapparatus according to Embodiment 1 of the present invention;

FIG. 7 illustrates frequency characteristics of variable coefficientfilter;

FIG. 8 is a block diagram showing a configuration of a variablecoefficient filter according to Embodiment 2 of the present invention;

FIG. 9 illustrates an example of a method of deciding tap coefficientAk;

FIG. 10 is a block diagram showing a configuration of a transmittingapparatus according to Embodiment 3 of the present invention;

FIG. 11 is a block diagram showing a configuration of pulse shapingfilter and variable coefficient filter according to Embodiment 3;

FIG. 12 illustrates an output waveform of pulse shape, variablecoefficient filter and addition operation section;

FIG. 13 is a block diagram showing a configuration of a transmittingapparatus according to Embodiment 3 of the present invention;

FIG. 14 is a block diagram showing a configuration of a transmittingapparatus according to Embodiment 3 of the present invention;

FIG. 15 is a block diagram showing a configuration of a transmittingapparatus according to Embodiment 3 of the present invention;

FIG. 16 is a block diagram showing a configuration of a transmittingapparatus according to Embodiment 3 of the present invention; and

FIG. 17 is a block diagram showing a configuration of a wirelesscommunicator provided with a transmitting apparatus of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below in detailwith the accompanying drawings.

Embodiment 1

FIG. 6 illustrates a configuration of the transmitting apparatusaccording to Embodiment 1 of the present invention.

Transmitting apparatus 100 of the present embodiment is formed withtransmission data signal input terminal 101, I signal generating section102, Q signal generating section 103, amplitude signal voltagegenerating section 104, phase modulation wave generating section 105,power amplifying section 106 and transmission output terminal 107.

I signal generating section 102 is formed with pulse generating section108 and variable coefficient filters 110 and 111. Q signal generatingsection 103 is formed with pulse generating section 109 and variablecoefficient filters 112 and 113.

In I signal generating section 102, pulse generating section 108converts a transmission data signal inputted from transmission datasignal input terminal 101 into an I component pulse signal Ip(t) andtransmits this I component pulse signal Ip(t) to variable coefficientfilters 110 and 111. Output I1(t) of variable coefficient filter 110 istransmitted to amplitude signal voltage generating section 104 andoutput I2(t) of variable coefficient filter 111 is transmitted to phasemodulation wave generating section 105.

In Q signal generating section 103, pulse generating section 109converts a transmission data signal inputted from transmission datasignal input terminal 101 into a Q component pulse signal Qp(t) andtransmits this Q component pulse signal Qp(t) to variable coefficientfilters 112 and 113. Output Q1(t) of variable coefficient filter 112 istransmitted to amplitude signal voltage generating section 104 andoutput Q2(t) of variable coefficient filter 113 is transmitted to phasemodulation wave generating section 105.

Amplitude signal voltage generating section 104 forms an amplitudecomponent modulation signal r(t) by performing the same processing as inabove-described amplitude signal voltage generating section 15 (FIGS. 1to 3 and FIG. 5) and transmits this to power amplifying section 106. Bythis means, the power supply voltage of power amplifying section 106 isset based on the amplitude component modulation signal r(t).

Phase modulation wave generating section 105 forms a phase componentmodulation signal Sc(t) by performing the same processing as in abovephase modulation wave generating section 16 (FIGS. 1 to 3 and FIG. 5)and transmits this to power amplifying section 106.

By performing the same processing as in above-described power amplifyingsection 17 (FIGS. 1 to 3 and FIG. 5), power amplifying section 106amplifies the signal acquired by multiplying power supply voltage valuer(t) of power amplifying section 106 and a phase component modulationsignal S_(c)(t) that is an output signal of phase modulation wavegenerating section 105, by gain G of power amplifying section 106, andoutputs this amplified signal as an RF vector modulation wave Srf(t).

Here, variable coefficient filters 110 to 113 employs a configurationhaving a pulse shaping filter that cancels intersymbol interferencebetween pulses and performs band-limitation. As an example of a pulseshaping filter, there is a filter with similar gain characteristics toroot cosine roll-off characteristics.

Further, variable coefficient filters 110 to 113 employ a configurationthat can change the transfer function coefficients. This transferfunction is the function that decides the frequency characteristics of afilter. Changing the coefficients of variable coefficient filters 110 to113 changes frequency characteristics of gain and group delay.

FIG. 7 illustrates an example of the frequency characteristics ofvariable coefficient filters 110 to 113. This example shows a case wherevariable coefficient filters 110 to 113 are digital filters and thesampling frequency in digital signal processing is 20 MHz, that is, thesampling period is 50 ns. FIG. 7A illustrates frequency characteristicsof gain and FIG. 7B illustrates frequency characteristics of groupdelay.

By changing the transfer function coefficients in variable coefficientfilters 110 to 113, the frequency characteristics change as shown by thesolid line, dash line and chain line in FIG. 7. FIG. 7 shows a case ofchanging transfer function coefficients so as to vary delay times as 95ns, 100 ns and 105 ns.

In frequency characteristics of group delay shown in FIG. 7B, the groupdelay shows approximately flat characteristics in the frequency domainin the range of around 2 MHz or less through which a signal passes, sothat it is possible to identify the delay times of 95 ns, 100 ns and 105ns from the group delay values in the domain.

In the examples of FIG. 7, the delay times are changed by 5 ns. Asdescribed above, the sampling period is 50 ns, and, consequently, thedelay time can be changed with precise resolution with compared to thesampling period.

Further, the gain frequency characteristics shown in FIG. 7A change alittle accompanying the change in the delay time. This change of theshape of frequency characteristics changes the shape of the frequencyspectrum of a signal that passes the above filters, and, as a result,causes the distortion in vector modulation wave Srf(t) outputted fromoutput terminal 107. However, as shown in FIG. 7A, the change of theshape of gain frequency characteristics accompanying the change in thedelay time is little, so that the deterioration of distortioncharacteristics stays within the allowable range for practical use.

Here, according to the present embodiment, the transfer functioncoefficient sequence for variable coefficient filter 110 and thetransfer function coefficient sequence for variable coefficient filter112 are set to the same numerical sequence. Further, the transferfunction coefficient sequence for variable coefficient filter 111 andthe transfer function coefficient sequence for variable coefficientfilter 113 are set to the same numerical sequence. Further, the transferfunction coefficient sequences for variable coefficient filters 110 and112 and the transfer function coefficient sequences for variablecoefficient filters 111 and 113 are made to change individually. Infact, when a delay difference needs to be adjusted, the transferfunction coefficient sequences for variable coefficient filters 110 and112, and the transfer function coefficient sequences for variablecoefficient filters 111 and 113 are set to different numerical values.

Thus, in transmitting apparatus 100, by changing the transfer functioncoefficients for variable coefficient filters 110 and 112 in the sameway as above, it is possible to adjust the delay time of an amplitudecomponent modulation signal r(t). Further, by changing the transferfunction coefficients for variable coefficient filters 111 and 113 inthe same way as above, it is possible to adjust a delay time of an phasecomponent modulation signal S_(c)(t). Therefore, by individuallychanging the coefficients for variable coefficient filters 110 and 112and the coefficients for variable coefficient filters 111 and 113, it ispossible to adjust the delay time difference between the amplitudecomponent modulation signal r(t) and the phase modulation signalS_(c)(t).

Changing the transfer function coefficient is realized by, for example,storing a plurality of coefficients in a memory and selecting andreading out the coefficient matching a designated delay time. Further,changing the transfer function coefficients can also be realized bycalculating and utilizing the coefficient matching the designated delaytime by a processor each time.

Next, the operations of transmitting apparatus 100 of the presentembodiment will be explained.

In transmitting apparatus 100, when there is a difference between thetime required to generate an amplitude component modulation signal r(t)in amplitude signal generating section 104 and the time required togenerate a phase component modulation signal Sc(t) in phase modulationwave generating section 105, distortion occurs in vector modulation waveSrt(t) outputted from power amplifying section 106.

Therefore, in transmitting apparatus 100, by adjusting the delay invariable coefficient filters 110 to 113, an amplitude componentmodulation signal r(t) and a phase component modulation signal Sc(t)without a delay difference are inputted to power amplifying section 106.In fact, the coefficients for variable coefficient filter 110 andvariable coefficient filter 112 are set to the same, and thecoefficients for variable coefficient filter 111 and variablecoefficient filter 113 are set to the same. Further, the coefficientsfor variable coefficient filters 110 and 112, and the coefficients forvariable coefficient filters 111 and 113, are set according to the delaydifference of processing between amplitude signal voltage generatingsection 104 and phase modulation generating section 105. For example,when the processing time in phase modulation wave generating section 105is longer than the processing time in amplitude signal voltagegenerating section 104, variable coefficient filters 110 to 113 are setsuch that output waves of variable coefficient filters 110 and 112 aredelayed by the above time difference more than output waves of variablecoefficient filters 111 and 113.

Here, these variable filters can precisely form waves compared to thesampling period of a signal, that is, these variable coefficient filterscan precisely adjust delay compared to the signal sampling period.Therefore, in transmitting apparatus 100, delay adjustment can beperformed at higher accuracy between an amplitude component modulationsignal r(t) and a phase component modulation signal S_(c)(t), so that itis possible to reduce the distortion of vector modulation wave Srf(t)outputted from power amplifying section 106 to a sufficiently low level.

As described above, according to the present embodiment, by providingvariable coefficient filters 110 and 112 in the preceding stage toamplitude signal voltage generating section 104, providing variablecoefficient filters 111 and 113 in the preceding stage to phasemodulation wave generating section 105, and by performing pulse shapingin variable coefficient filters 110 and 113 and performing delayadjustment for an amplitude component modulation signal r(t) and a phasecomponent modulation signal S_(c)(t), it is possible to adjust the delaytime difference between the amplitude component modulation signal r(t)and the phase component modulation signal S_(c)(t) with preciseresolution compared to the sampling period in signal processing. As aresult, it is possible to reduce the distortion of vector modulationwave Srf(t) to a sufficiently low level.

Embodiment 2

The present embodiment suggests using the FIR (Finite Impulse Response)filter shown in FIG. 8 for variable coefficient filters 110 to 113explained in Embodiment 1. Further, although FIG. 8 illustrates theconfiguration of variable coefficient filter 110, the configurations ofvariable coefficient filters 111, 112 and 113 are the same as in FIG. 8.

In FIG. 8, the transfer function coefficient, that is, the tapcoefficient is Ak (k is a natural number). A tap coefficient sequencematches the data sequence of an impulse response waveform expressed inthe discrete time. That is, the tap coefficient sequence is numericalvalues of the impulse response waveform expressed in the continuoustime.

As an example, FIG. 8 illustrates a configuration where the order of atransfer function, that is, the number of taps, is 33. In this case, therelationship between input signal data sequence X(n) and output signaldata sequence Y(n) is expressed by the following equation.

Y(n)=A0·X(n)+A1·X(n−1)+ . . . +A32·X(n−32)   (Equation 9)

FIG. 9 is a schematic view illustrating a state where impulse responsewaveforms are sampled to acquire the value of tap coefficient Ak. FIGS.9A and 9B show the method of determining tap coefficient Ak for changingdelay time.

In FIG. 9A, the impulse response waveform shown by the dash line issampled at a regular period and is data sequences shown with dots.Further, the value of each data at vertical axis shown with dots is setas tap coefficient Ak in the FIR filter. The sampling period upon thissampling matches the sampling period in digital signal processing in theFIR filter.

On the other hand, in FIG. 9B, the impulse response waveform shown bythe dash line is sampled at a regular period and is set as tapcoefficient An in the FIR filter. However, compared to FIG. 9A, althoughthe impulse response waveform shown by the dash line is the same in theform, the impulse response waveform is different in shifting in the timedomain. This shows that the same impulse response waveform is sampled atdifferent sampling timings, that is, the same impulse response waveformis sampled in different sampling phases.

Therefore, the values of tap coefficient Ak are different between FIG.9A and FIG. 9B. However, the original impulse response waveforms shownby the dash line are the same, that is, although there is no essentialdifference between the pass characteristics of a signal, there is adifference in shifts in the time domain, that is, there is a differencein delay time. Therefore, by using the FIR filter, it is possible tochange delay time alone without changing the gain frequencycharacteristics.

As shown in FIG. 9B, compared to FIG. 9A, the delay time in the FIRfilter where tap coefficient Ak acquired by sampling is set as shown inFIG. 9B, is half the sampling period, that is, the delay time is halfthe sampling period in signal processing. That is, upon changing the tapcoefficient, by using the tap coefficient acquired by the above method,it is possible to change the delay time with precise resolution comparedto the sampling period in signal processing.

For ease of explanation, although an example has been described in FIG.9 where the resolution for adjusting delay time is half the samplingperiod, it is possible to adjust resolution more precisely depending ona method of selecting a sampling phase to acquire tap coefficients.

Here, for example, when the processing time in phase modulation wavegenerating section 105 is longer than the processing time in amplitudesignal voltage generating section 104 by half the sampling period, tapcoefficients A0 to A32 in variable coefficient filters 110 and 112employing a configuration of the FIR filter may be set as shown in FIG.9B, and tap coefficients A0 to A32 in variable coefficient filters 111and 113 employing a configuration of the FIR filter may be set as shownin FIG. 9A.

Further, changing tap coefficients is realized by, for example, storinga plurality of tap coefficients in a memory and selecting and readingout the coefficient matching the designated delay time. Further,changing tap coefficients can also be realized by calculating andutilizing the coefficient matching the designated delay time by aprocessor each time.

As described above, according to the present embodiment, by using an FIRfilter as variable coefficient filters 110 to 113, it is possible toadjust the delay time difference between an amplitude componentmodulation signal r(t) and a phase component modulation signal S_(c)(t)with precise resolution compared to the sampling period in signalprocessing. As a result, it is possible to reduce the distortion ofvector modulation wave Srt(t) to a sufficiently low level.

Embodiment 3

FIG. 10 has the same components shown in FIG. 6 and assigned the samenumerical numbers as in FIG. 6, and illustrates a configuration of thetransmitting apparatus of the present embodiment.

I signal generating section 201 of the transmitting apparatus 200 isformed with pulse generating section 108 and pulse shaping filter 203.Similarly, Q signal generating section 202 is formed with pulsegenerating section 109 and pulse shaping filter 204. Further, intransmitting apparatus 200, variable coefficient filters 205 and 207 areprovided in the preceding stage to amplitude signal voltage generatingsection 104 and variable coefficient filters 206 and 208 are provided inthe preceding stage to phase modulation wave generating section 105.

In transmitting apparatus 200, the output of pulse shaping filter 203and the output of variable coefficient filter 205 are summed up inaddition operation section 209 and inputted to amplitude signal voltagegenerating section 104, and the output of pulse shaping filter 204 andthe output of variable coefficient filter 207 are summed up in additionoperation section 211 and inputted to amplitude signal voltagegenerating section 104. Further, in transmitting apparatus 200, theoutput of pulse shaping filter 203 and the output of variablecoefficient filter 206 are summed up in addition operation section 210and inputted to phase modulation wave generating section 105, and theoutput of pulse shaping filter 204 and the output of variablecoefficient filter 208 are summed up in addition operation section 212and inputted to phase modulation wave generating section 105.

Here, compared to transmitting apparatus 100 of FIG. 6, transmittingapparatus 200 of the present embodiment employs a configuration furtherhaving pulse shaping filters 203 and 204 and addition operation sections209 to 212. By adding these components, in transmitting apparatus 200,compared to variable coefficient filters 110 to 113 (FIG. 6), the pulseshaping filter functions are removed from variable coefficient filters205 to 208.

FIG. 11 illustrates the configuration of pulse shape filter 203 andvariable coefficient filter 205. Further, the configuration of pulseshape filter 204 and variable coefficient filters 206, 207 and 208 willbe the same as in FIG. 11.

Pulse shaping filters 203 and 204 are FIR filters and have tapcoefficient Ck (k is a natural number). Variable coefficient filters 205to 208 are FIR filters and have tap coefficient Bk (k is a naturalnumber).

FIG. 11 illustrates an example of a configuration where the number oftaps is 33. In this case, the relationship between input signal datasequence X(n) and output signal data sequence Y(n) is expressed by thefollowing equation.

Y(n)=B0·X(n)+B1·X(n−1)+ . . . +B32·X(n−32)+C0·X(n)+C1·X(n−1)+ . . .+C32·X(n−32)   (Equation 10)

When the right side of equation 10 is expanded, the following equationis acquired.

(B0+C0)·X(n)+(B1+C1)·X(n−1)+ . . . +(B32+C32)·X(n−32)   (Equation 11)

When equation 11 is compared to equation 9 explained in Embodiment 2, ifthe following equation is established, the transfer characteristics arethe same.

Ak=Bk+Ck   (Equation 12)

Equation 12 can be changed into the following equation.

Bk=Ak−Ck   (Equation 13)

The same coefficient as in a conventional pulse shaping filter may beset as the coefficient in pulse shaping filters 203 and 204. That is,coefficients such as tap coefficient Ck (k is a natural number)explained using equation 8 as a conventional example, may be set.

Further, Ak (k is a natural number) is the tap coefficient for variablecoefficient filters 110, 111, 112 and 113 explained in Embodiment 2.

Therefore, according to the present embodiment, as shown in equation 13,the difference is calculated between the value of Ak determined inaccordance with the desirable delay time and the value of tapcoefficient Ck for pulse shaping filters 203 and 204, and thiscalculated difference is set as tap coefficient Bk for variablecoefficient filters 205, 206, 207 and 208.

Here, in transmitting apparatus 200, by changing the tap coefficient forvariable coefficient filters 205 and 207 in the same way as above, thedelay time for an amplitude component modulation signal r(t) isadjusted. Further, by changing the tap coefficient for variablecoefficient filters 206 and 208, the delay time for a phase componentmodulation signal S_(c)(t) is adjusted. Further, by changing the tapcoefficient for variable coefficient filters 205 and 207 and the tapcoefficient for variable coefficient filters 206 and 208 individually,the delay time difference between the amplitude component modulationsignal r(t) and the phase component modulation signal Sc(t). In fact,when a delay difference needs to be adjusted, the tap coefficients forvariable coefficient filters 205 and 207 and the tap coefficients forvariable coefficient filters 206 and 208 are set to be different.

Changing a tap coefficient is realized by, for example, storing aplurality of tap coefficients in a memory and selecting and reading outthe coefficient matching a designated delay time. Further, changing atap coefficient can also be realized by calculating and utilizing thecoefficient matching the designated delay time by the processor eachtime.

Next, FIG. 12A illustrates an output waveform in pulse shaping filter203, FIG. 12B illustrates an output waveform in variable coefficientfilter 205 and FIG. 12C illustrates an output waveform in additionoperation section 209. Here, an output waveform in pulse shaping filter204 is the same as in FIG. 12A, an output waveform in variablecoefficient filter 207 is the same as in FIG. 12B and an output waveformin addition operation section 211 is the same as in FIG. 12C. Further,output waveforms in variable coefficient filters 206 and 208 areacquired by changing the waveform in FIG. 12B by the delay time, andoutput waveforms in addition operation sections 211 and 212 are acquiredby shifting the waveform in FIG. 12C by the delay time in the timedomain.

With the above present embodiment, by adjusting the delay between anamplitude component modulation signal r(t) and a phase modulation signalS_(c)(t) using pulse shaping filters 203 and 204 and variablecoefficient filters 205 to 208, compared to a case where delayadjustment is performed using variable coefficient filters 110 to 113alone as shown in Embodiment 1, by leaving pulse shaping processing topulse shaping filters 203 and 204, (i.e., by producing a component ofthe difference alone in variable coefficient filters 205 to 208, whichis equivalent to delaying a signal), variable coefficient filters 205 to208 can perform delay adjustment much more accurately than withEmbodiment 1 or perform delay adjustment equivalent to the delayadjustment in Embodiment 1 with a much simpler configuration than withEmbodiment 1.

That is, as shown in FIG. 12B, with the present embodiment, by leavingpulse shaping processing to pulse shaping filters 203 and 204, theoutput level of variable coefficient filters 205 to 208 becomes low.Therefore, if the number of bits of tap coefficients is the same betweenvariable coefficient filters 205 to 208, it is possible to improve theaccuracy at the level axis. By contrast, if the accuracy at the levelaxis needs not be improved, the number of bits of tap coefficients canbe reduced, so that it is possible to simplify the configuration.

Here, as pulse shaping filters 203 and 204, an existing pulse shapingfilter can be used, so that costs will not increase for new development,designing and production. That is, delay time adjustment can be realizedwith good characteristics using a pulse shaping filter mounted on aconventional transmitting apparatus as a fixed coefficient filter. Here,although pulse shaping filters 203 and 204 are sufficient to be filterswith fixed coefficients, pulse shaping filters 203 and 204 may befilters with variable coefficients.

As described above, according to the present embodiment, by providingpulse shaping filters 203 and 204 and variable coefficient filters 205to 208, and by producing a component of the difference alone in variablecoefficient filters 205 to 208, which is equivalent to delaying asignal, and adding the signal to an output signal of pulse shapingfilters 203 and 204, in addition to the advantageous of Embodiments 1and 2, it is possible to perform delay adjustment much more accuratelythan with Embodiments 1 and 2 or perform delay adjustment equivalent tothe delay adjustment in Embodiments 1 and 2 with a much simplerconfiguration than with Embodiments 1 and 2.

Further, in the configuration of FIG. 10, although both advancing anddelaying an amplitude component modulation signal r(f) and advancing anddelaying a phase component modulation signal Sc(t) are possible, toadjust the delay time difference between the amplitude component and thephase component, advancing and delaying one of these components aloneneeds to be performed. Therefore, the variable coefficient filters thatprocess one of the amplitude component and the phase component can bereplaced with the fixed coefficient filters.

For example, FIGS. 13 and 14 illustrate other configurations of thetransmitting apparatus according to the present embodiment. Transmittingapparatus 200A of FIG. 13 shows an example where variable coefficientfilters 206 and 208 of FIG. 10 are replaced with fixed coefficientfilters 213 and 214 so that an amplitude component modulation signalr(t) alone can be advanced and delayed. Transmitting apparatus 200B ofFIG. 14 shows an example where variable coefficient filters 205 and 207of FIG. 10 are replaced with fixed coefficient filters 215 and 216 sothat a phase component modulation signal Sc(t) alone can be advanced anddelayed. Generally, compared to providing a variable coefficient filter,a fixed coefficient filter can be provided with fewer devices, so thatit is possible to reduce the circuit scale and power consumption.

Further, FIGS. 15 and 16 illustrate other configurations of thetransmitting apparatus according to the present embodiment. Transmittingapparatus 200C of FIG. 15 shows an example where fixed coefficientfilters 213 and 214 and addition operation sections 210 and 212 of FIG.13 are removed so that an amplitude component modulation signal r(t)alone can be advanced and delayed. Transmitting apparatus 200D of FIG.16 shows an example where fixed coefficient filters 215 and 216 andaddition operation sections 209 and 211 of FIG. 14 are removed so that aphase component modulation signal Sc(t) alone can be advanced anddelayed. By removing fixed coefficient filters, it is possible tofurther reduce the circuit scale and power consumption.

Other Embodiments

FIG. 17 illustrates a schematic configuration of a radio communicationdevice employing transmitting apparatus 100 (200) according toEmbodiments 1 to 3. Radio communication device 300 is formed withtransmitting apparatus 100 (200) according to one of Embodiments 1 to 3,receiving apparatus 301 that acquires received data by performingpredetermined reception processing including demodulation processing ona received signal, duplexer 302 that switches a transmission signal andreceived signal, and antenna 303.

By this means, radio communicator 300 employs a configuration having thetransmitting apparatus of the present invention, and, consequently, cantransmit the RF vector modulation wave with less distortion. As aresult, for example, if radio communicator 300 is a mobile terminal, itis possible to realize a mobile terminal that can be used for a longtime and transmit a high quality transmission signal.

The disclosure of Japanese Patent Application No. 2005-375417, filed onDec. 27, 2005, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The transmitting apparatus of the present invention provides advantageof reducing distortion of a vector modulation wave that is atransmission output, and is applicable and useful to for example, mobiletelephone devices.

1-21. (canceled)
 22. A transmitting apparatus comprising: a first pulsegenerating section that generates an in-phase component pulse signal; asecond pulse generating section that generates a quadrature componentpulse signal; a first pulse shaping filter that receives the in-phasecomponent pulse signal as an input signal; a second pulse shaping filterthat receives the quadrature component pulse signal as an input signal;a first variable coefficient filter that receives the in-phase componentpulse signal as an input signal; a second variable coefficient filterthat receives the quadrature component pulse signal as an input signal;a first addition operation section that adds an output signal of thefirst pulse shaping filter and an output signal of the first variablecoefficient filter and outputs this added signal as a first in-phasecomponent modulation signal; a second addition operation section thatadds an output signal of the second pulse shaping filter and an outputsignal of the second variable coefficient filter and outputs this addedsignal as a first quadrature component modulation signal; an amplitudesignal voltage generating section that generates an amplitude componentmodulation signal using a combination of the first in-phase componentmodulation signal and the first orthogonal modulation signal or acombination of an output signal of the first pulse shaping filter and anoutput signal of the second pulse shaping filter; a phase modulationwave generating section that generates a phase modulation wave using asignal not used in the amplitude signal voltage generating section inthe combination of the first in-phase component modulation signal andthe first orthogonal modulation signal or the combination of the outputsignal of the first pulse shaping filter and the output signal of thesecond pulse shaping filter; and a power amplifying section thatgenerates a vector modulation wave acquired by amplitude-modulating thephase modulation wave in the amplitude component modulation signal. 23.The transmitting apparatus according to claim 22, wherein the first andsecond variable coefficient filters are finite impulse response filters.24. The transmitting apparatus according to claim 23, wherein a transferfunction coefficient sequence in the first and second variablecoefficient filters is a numerical sequence of a difference between anumerical sequence acquired by sampling an impulse response waveform bya first sampling phase and a numerical sequence acquired by sampling theimpulse response waveform by a second sampling phase different from thefirst sampling phase.
 25. The transmitting apparatus according to claim22, wherein a transfer function coefficient sequence for the firstvariable coefficient filter and a transfer function coefficient sequencefor the second variable coefficient filter are the same numerical value.26. The transmitting apparatus according to claim 22, further comprisinga memory that stores coefficient sequences that are used for transferfunction coefficient sequences for the first and second coefficientvariable filters and that match respective predetermined delay times.27. The transmitting apparatus according to claim 22, further comprisinga processor that processes coefficient sequences that are used fortransfer function coefficient sequences in the first and secondcoefficient variable filters and that match respective predetermineddelay times.
 28. A radio communicator comprising: the transmittingapparatus according to claim 22; a receiving apparatus that demodulatesa received signal; an antenna; and a transmission/reception switchingsection that switches a supply of the vector modulation wave from thetransmitting apparatus to the antenna and a supply of the receivedsignal from the antenna to the receiving apparatus.
 29. A transmittingapparatus comprising: a first pulse generating section that generates anin-phase component pulse signal; a second pulse generating section thatgenerates a quadrature component pulse signal; a first pulse shapingfilter that receives the in-phase component pulse signal as an inputsignal; a second pulse shaping filter that receives the quadraturecomponent pulse signal as an input signal; a first variable coefficientfilter that receives the in-phase component pulse signal as an inputsignal; a second variable coefficient filter that receives thequadrature component pulse signal as an input signal; a third variablecoefficient filter that receives the quadrature component pulse signalas an input signal; a fourth variable coefficient filter that receivesthe quadrature component pulse signal as an input signal; a firstaddition operation section that adds an output signal of the first pulseshaping filter and an output signal of the first variable coefficientfilter and outputs this added signal as a first in-phase componentmodulation signal; a second addition operation section that adds theoutput signal of the first pulse shaping filter and an output signal ofthe second variable coefficient filter and outputs this added signal asa second in-phase component modulation signal; a third additionoperation section that adds an output signal of the second pulse shapingfilter and an output signal of the third variable coefficient filter andoutputs this added signal as a first quadrature component modulationsignal; a fourth addition operation section that adds the output signalof the second pulse shaping filter and an output signal of the fourthvariable coefficient filter and outputs this added signal as a secondquadrature component modulation signal; an amplitude signal voltagegenerating section that generates an amplitude component modulationsignal from the first in-phase component modulation signal and the firstorthogonal modulation signal; a phase modulation wave generating sectionthat generates a phase modulation wave from the second in-phasecomponent modulation signal and the second orthogonal modulation signal;and a power amplifying section that generates a vector modulation waveacquired by amplitude-modulating the phase modulation wave in theamplitude component modulation signal.
 30. The transmitting apparatusaccording to claim 29, wherein the first, second, third and fourthvariable coefficient filters are finite impulse filters.
 31. Thetransmitting apparatus according to claim 30, wherein a transferfunction coefficient sequence in the first, second, third and fourthvariable coefficient filters is a numerical sequence of a differencebetween a numerical sequence acquired by sampling an impulse responsewaveform by a first sampling phase and a numerical sequence acquired bysampling the impulse response waveform a second sampling phase differentfrom the first sampling phase.
 32. The transmitting apparatus accordingto claim 29, wherein: a transfer function coefficient sequence in thefirst variable coefficient filter and a transfer function coefficientsequence in the third variable coefficient filter are the same numericalsequence; a transfer function coefficient sequence for the secondvariable coefficient filter and a transfer function coefficient sequencefor the fourth variable coefficient filter are the same numericalsequence; and the transfer function coefficient sequence for the firstvariable coefficient filter and the transfer function coefficientsequence for the third variable coefficient filter are differentnumerical sequences from the transfer function coefficient sequence forthe second variable coefficient filter and the transfer functioncoefficient sequence for the fourth variable coefficient filter.
 33. Thetransmitting apparatus according to claim 29, further comprising amemory that stores coefficient sequences that are used for a pluralityof transfer function coefficient sequences in the first, second, thirdand fourth coefficient variable filters and that match respectivepredetermined delay times.
 34. The transmitting apparatus according toclaim 29, further comprising a processor that processes coefficientsequences that are used for a plurality of transfer function coefficientsequences in the first, second, third and fourth coefficient variablefilters and that match respective predetermined delay times.
 35. A radiocommunicator comprising: the transmitting apparatus according to claim29; a receiving apparatus that demodulates a received signal; anantenna; and a transmission/reception switching section that switches asupply of the vector modulation wave from the transmitting apparatus tothe antenna and a supply of the received signal from the antenna to thereceiving apparatus.